Throughout history, people have sought more comfortable seating arrangements. Chairs, stools, and the like allow people to relieve stress on the legs and feet, while remaining alert and performing tasks that do not require a great deal of motion. In the twentieth century, folding chairs have made it possible for people to keep a space clear when necessary, and to erect suitable seating for gatherings or special events. However, current folding chairs possess a number of drawbacks.
Folding chairs of a variety of configurations are known in the art. Indeed, an intended advantage of folding chairs is that, in a folded state, they may be shipped or stored more conveniently than non-folding or fully assembled chairs. Conventional folding chairs generally include a backrest frame having legs that extend at downward angles to become the front legs of the chair, back legs pivotally mounted to the back rest frame, and a seat frame pivoted to the backrest frame, and the back legs. In addition, the prior art is replete with a wide variety of hinge and joint configurations to support and guide the folding members.
While the folding chairs of the prior art fulfill their respective objectives, the folding chair configurations of the prior art often sacrifice stability and durability relative to traditional, non-folding chairs, to achieve their respective functions. Accordingly, a need exists in the art for a folding chair that erects into a stable from approximating traditional, non-folding chairs. Embodiments of the present invention substantially fulfill this need.
The inventor has found that folding chairs are often somewhat heavy. The chair must reliably support the weight of even a fairly large person. The bending stress on any member is proportional to the length of the member multiplied by the force acting upon it. Therefore, the length of the seat effectively multiplies the forces tending to bend or break the seat. Typically, seats for folding chairs have been made from stronger (and heavier) materials, such as steel, to overcome the effect of these bending stresses. The resulting chairs are heavier and therefore cost more to ship, and require more effort to move, fold, and unfold.
Thus, it is desirable to use lightweight materials such as plastics to reduce the weight of folding chairs. However, many known folding chairs, especially those that incorporate lightweight materials, do not stand up to repetitive use. Groups such as the business and institutional furniture manufacturers' association have set up standards for portable furniture. Such standards typically require that portable chairs be designed to receive a given weight loading to simulate use for a specified number of cycles, often on the order of 100,000. Many known folding chairs bend or break after only a few thousand cycles, and therefore can be expected to have a relatively short useful life.
Still further, many known folding chairs are somewhat expensive to produce because the manner in which they are assembled requires the use of a great deal of manual labor. The legs must often be properly aligned with the seat so that mechanical fasteners can be attached to the legs and the seat. If metal supporting parts are to be threaded through the lightweight seat member to connect the legs, the lightweight seat member may have to be aligned with each leg assembly so that the threading operation can be carried out. Often, the various fasteners involved must be installed at locations that are not easily accessible for machinery. Thus, the fasteners must often be installed by hand.
Accordingly, a need exists for a portable, folding chair that is lightweight and comfortable, and yet folds to a thin, stackable configuration. Such a chair must safely support the weight of a fairly heavy person. In addition, the chair should be inexpensive to produce in large quantities with a minimum of parts and assembly.